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Fluttering to Extinction?

Lange's MetalmarkThis story by Jim Nickles was originally published in the Spring 2007 issue of Tideline, the quarterly newsletter of the San Francisco Bay National Wildlife Refuge Complex.

Preventing the Lange's Metalmark Butterfly From Floating Away

The Lange’s metalmark butterfly, whose only home is a few stunted sand mounds in the Contra Costa County town of Antioch, is fluttering dangerously close to extinction.

But conservationists are working to bring it back from the brink.

The U.S. Fish and Wildlife Service has launched an aggressive new effort to restore habitat at Antioch Dunes National Wildlife Refuge, its only known home, and breed the species in captivity until its wild population can be stabilized and, eventually, recovered to full health.

The new effort is a joint project of the refuge and the Fish and Wildlife Service’s Ecological Services program in Sacramento, with the help of a lot of partners and volunteers. The Service is working with the San Diego Zoo and others to establish the captive-breeding program and with Pacific Gas & Electric Co. to improve habitat on PG&E-owned land that is part of the refuge.

“We have been very concerned about the butterfly population at Antioch Dunes National Wildlife Refuge and are taking some positive actions that we hope will be successful in helping the population to recover,” said Mendel Stewart, project leader for the San Francisco Bay National Wildlife Refuge Complex, which includes Antioch Dunes.

“The Service and its partners are undertaking a renewed effort to protect the habitat and ensure the survival of the species, through habitat restoration and enhancement, and captive propagation of the butterfly,” said Craig Aubrey, leader of the endangered species recovery team at the Service’s Sacramento field office.

 

Lange's Metalmark Butterfly OvipositingThe two-pronged approach – habitat improvements and captive-breeding – has worked to stabilize the population of the endangered Palos Verdes blue butterfly, a Southern California species once thought to be extinct. Conservationists hope to show equal success with the Lange’s metalmark butterfly.

One of the first insects to be protected by the Endangered Species Act, the Lange’s metalmark has been federally listed as endangered since 1976. It is a fragile, brightly colored butterfly in the Riodinidae (metalmark) family, with an adult wingspan that varies from 1 to 1 1/2 inches.

Metalmark butterflies are named for their grey, or metallic-colored, spots on their wings. Three other species of metalmark butterflies are found throughout California, but this particular subspecies is named for the late William H. Lange Jr., the young UC Berkeley entomology student – and future UC Davis professor – who first described it in the 1930’s.

Unlike some butterflies that can travel for hundreds of miles, the Lange’s metalmark is not known to have ever ventured beyond the sand dunes along the southern bank of the San Joaquin River, on the far western edge of the Sacramento-San Joaquin Delta. Now, with most of those dunes long gone, the butterfly’s only remaining habitat is at the Antioch Dunes National Wildlife Refuge.

Also unlike some other butterflies that can produce more than one generation in a year, the Lange’s metalmark produces only one crop of young per year. Each summer’s count of adult butterflies is considered a critical indicator of the species’ health.

Unfortunately, those counts have been on decline for the last several years. While the falling numbers prompted growing concern among refuge managers and endangered species biologists, the most recent results set off alarm bells.

Last fall, biologists recorded a peak count of only 45 adult Lange’s metalmark butterflies, down from 232 in 2005 and a high of 2,342 in 1999.

“That of course is of great concern,” said consulting biologist Dr. Travis Longcore, who proposed the captive-breeding program as a way to ensure the butterfly’s survival. “You have a species declining, but we don’t know why.”

Longcore is science director of the Urban Wildlands Group, a non-profit conservation organization based in Los Angeles that has overseen the captive-propagation of the Palos Verdes blue butterfly.

He and others say several factors are likely to blame for the Lange’s metalmark’s rapid decline. They include a continuing invasion of exotic weeds at the refuge that are choking out the butterfly’s host plant, the naked-stem buckwheat. Several large arson fires in recent years killed both buckwheat and butterflies.

“Fires killed a lot of the host plants and they killed a lot of the butterflies,”Aubrey said. “That, combined with the threat of invasives, has hit the species pretty hard.”

Early MiningDespite its name, few actual dunes remain at the refuge, and they are pale reminders of what was once there. In the 19th Century, shifting dunes up to 100 feet high dominated the south bank of the river for more than two miles. Over the course of many decades, the dunes disappeared, their sand mined to build California’s highways and houses, including many buildings in San Francisco.

These days, the refuge’s rolling swales and flatlands are carpeted with a host of non-native plants, including yellow star thistle, Russian thistle, vetch and non-native grasses like ripgut brome.

The 67-acre refuge - divided into two units owned by the Service and 12 acres of adjacent land owned by PG&E - is a “biological island” of rare and exotic plants and insects that are found nowhere else in the world. The refuge was established in 1980 as a haven for two federally listed endangered plants – the Contra Costa wallflower and the Antioch Dunes evening primrose – as well as the Lange’s metalmark butterfly.

“That is literally the last remaining habitat anywhere (for Lange’s),” Aubrey said. “That is what makes this refuge so special.”

The task facing the refuge is how to save dune-dependent native plants – and the butterfly that depends on them -- when functioning sand dunes no longer exist. The native plants need the shifting sand, steep banks and clear ground of real dunes. But the increasingly thick weed base stabilizes the soil, which in turn leads to the growth of more weeds.

The refuge has tried several tactics to control the weeds, prevent fires and encourage the growth of endangered plants. Those tactics have probably not been aggressive enough, as the explosion of vetch has demonstrated, refuge manager Christy Smith said.

Vetch, the refuge’s new worst culprit, covers the ground with a thick carpet, choking out such plants as the naked-stem buckwheat, which the butterfly uses. Pulling the vetch out is difficult, because it intertwines with other plants.

“Vetch is just horrible because as it grows it covers and encapsulates other plants, such as the host plant for the butterfly, and creates an unsuitable micro-climate for the life cycle of the butterfly,” Smith said. “Vetch attaches to other plants with tendrils that make it difficult to pull or remove without damaging buckwheat or stripping larvae or eggs from the buckwheat.”

The refuge is preparing an updated Endangered Species Act report known as a Biological Opinion that outlines a new plan of action – for more fire breaks, more land cleared of weeds, more plantings of nursery-raised native plants, and more monitoring and evaluation of various tactics. The plan calls for clearing and improving 10 acres of habitat each year – twice as many acres as in the past.

Volunteer Michael Krieg plants a young crop of Contra Costa wallflowers on the refugeIn December, refuge biologists Susan Euing and Louis Terrazas led a group of volunteers that planted hundreds of young Contra Costa wallflowers on some steep sand hills that had been recently cleared of weeds.

“It really likes these slopes,” said volunteer Michael Krieg as stooped to put the fragile young plants in their new home. “It doesn’t do well in the flats.”

As they work the habitat and battle vetch, Smith and her team will assess what works and what does not. Among other things, they will be testing different methods of controlling the weeds by hand, heavy equipment or chemicals. They might even try grazing on a limited basis.

Just as important as habitat improvements will be the effort to breed Lange’s metalmark butterflies in captivity. To fund the work, Aubrey’s endangered-species recovery program recently applied for a $250,000 federal grant from the Central Valley Project Conservation Program. Those grants will be awarded later this spring.

Not everyone is convinced that the Lange’smetalmark butterfly can be bred in captivity. Jerry Powell, a retired UC Berkeley entomology professor who has studied the Lange’s metalmark for more than 20 years, said the butterfly presents unique challenges because of its restricted habitat requirements and long breeding season – and the fact that it produces only one generation per year.

Adult Lange’s metalmarks lay their eggs at the base of buckwheat stems in the late summer, and the eggs remain dormant until the rainy season begins in late fall or early winter. The larvae that emerge begin feeding on the new growth of the buckwheat plant, but they don’t transform from caterpillars into butterflies until mid- to late summer.

Others say that, while captive-breeding success is not guaranteed, it is one option they need to try to prevent the species from going extinct.

Captive breeding of Lange’s has worked on a limited basis, said Longcore, whose Urban Wildlands Group has agreed to develop procedures for the breeding program. If funding is approved, the breeding would be conducted at the San Diego Zoo’s Beckman Center for Conservation Research in Escondido.

“I just think this is the one right choice we can make right now that puts us on the path to be successful,” Longcore said.

For now, biologists are crossing their fingers that a new generation of Lange’s metalmark butterflies emerges this summer. They hope to capture at least five adult females, and then transfer them to the Beckman Center in potted buckwheat plants. In netted enclosures at the center, hatched larvae will be raised to the pupae stage, then transported back to the refuge and placed at the base of buckwheat plants.

Eventually, as the habitat for the butterfly improves, the natural population will grow and become self-sustaining.

Or at least that is the plan.

“We hope that this comprehensive approach, which involves restoration and captive breeding and developing public-private partnerships, leads to the recovery of Lange’s and the two plants,” Aubrey said. “We want those species to be here for future generations.”

Jim Nickles was the deputy chief of external affairs for the Sacramento Fish and Wildlife Office until 2007. He is now with the U.S. Geological Survey’s California Water Science Center in Sacramento.   

Page Photo Credits — Butterfly Ovipositing / FWS, Historic Mining / FWS, Volunteer Michael Krieg Planting Wallflowers / FWS
Last Updated: Jan 02, 2013
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